应用有机相法制备钒磷复合氧化物,并通过浸渍法引入Ce,Te,Nb添加组分。采用低温氮吸附-脱附、XRD、TPR等手段进行了表征。结果表明,采用浸渍法制备的M-VPO(M=Ce,Te,Nb)其主要晶相为焦磷酸氧钒[(VO)2P2O7]。催化剂的性能与添加组分的种类和含量密切相关。不同添加组分及含量明显改变了样品的微观结构及氧化还原能力,进而影响其催化反应行为。
The VPO catalysts prepared in organic media were doped with Te, Ce and Nb in different loadings via impregnation method. The dopants with higher contents enhanced oxidation ability of the catalyst, especially for the Te doped one. HE-TPR results indicate that the reactivity of M-VPO lattice shows the following trend: Ce-VPO-Nb- VPO〈Te-VPO. However, the conversion of propane does not simply follow this tendency, suggesting that activation and conversion of propane is closely related to certain lattice oxygen in catalysts. The dispersion of dopants over VPO base varies with dopant content, and consequently, influences the dopant-VPO interaction, which in turn affects the catalytic behavior of the catalyst: (a) Nb dopant significantly increases the reactivity of the catalyst, but notably decreases the selectivity to AA owing to the enhanced deep oxidation; (b) the lattice oxygen associated with Te dopant may involve the oxygen insertion reaction to generate acrylic acid (AA) product, thus increases the AA selectivity; (c) the Ce dopant with high concentration also increases deep oxidation of the catalyst. However, the appropriate amount of Ce dopant(nce:nv=0.02) shows a promotion effect on AA formation.